The invention relates to a dryer section for a machine for the production or processing of fibrous webs, in particular paper webs, of the type having the following features
(a) several heatable drying cylinders arranged in two rows one above the other so that the fibrous web meanders through the dryer section;
(b) to the top row of cylinders is allotted a top supporting belt and to the bottom row of cylinders a bottom supporting belt, with each supporting belt running in the direction of web travel behind a drying cylinder over a carrier roll;
(c) in at least one part of the pockets, of which each is delimited by the free peripheral part of a drying cylinder, by the opposite carrier roll and by the fibrous web is provided a device for the contactless stabilization of the run of the fibrous web ("web stabilizer"); and
(d) the web stabilizer comprises at least one nozzle element extending transversely across the width of the web and connected to a supply-air pipe, which exhibits an air blow slot open towards the fibrous web and a web-guiding surface interacting with it.
Such a dryer section is known from German Pat. Document No. 36 30 571.
The web stabilizer used in this known dryer section includes a blow box with approximately trapezoidal cross-section The main feature of this blow box is that there are two blow nozzles acting in opposite directions at its web-guiding surface. Thus one blow nozzle blows in the direction of web travel, and the other in the opposite direction. Each of the two air jets flows (viewed in the cross-section) in the direction towards the end of the web-guiding surface and thereafter into the atmosphere, i.e., into the internal space, also called "pocket", which is delimited by the free peripheral section of one of the drying cylinders, by the opposite carrier roll and by the fibrous web which runs on one side onto the said cylinder and on the other side runs off it. Although it is desired that a certain overpressure should exist in such a pocket, with the known arrangement there is a danger that this overpressure will assume too high a value.
From the aforementioned reference no. 36 30 571 it is also known (FIG. 7) for a carrier roll to be arranged at least one of the drying cylinders in such a way that its periphery is, at a certain distance from the exiting point of the fibrous web from the drying cylinder, tangent to the running path of the fibrous web. In this connection it is of importance that the different embodiments of the web stabilizer known from reference no. 36 30 571 have the common feature that they are arranged on that side of the fibrous web which contacts the subsequent drying cylinders. The aim of this is that the web stabilizer should draw the fibrous web "firmly against the surface of the dryer fabric" by means of suction.
According to reference no. 36 30 571 the aim is also to make the length of the web stabilizer, viewed in the cross-section, as large as possible so that the free (unsupported) areas of the fibrous web are relatively short.